{"product_id":"gm-powermaster-31487-chrome-220a-6-grv-alt","title":"GM Powermaster 31487 Chrome 220A 6 grv Alt","description":"\u003cp\u003eThe only alternator rating most people are familiar with is the amperage rating.\u003c\/p\u003e\u003cp\u003eAlternators are referred to as a 65 amp or 100 amp alternator.\u003c\/p\u003e\u003cp\u003eWhen replacing the alternator on the family car, this is likely the only information necessary.\u003c\/p\u003e\u003cp\u003eAfter all, an alternator that matches the original is all one needs.\u003c\/p\u003e\u003cp\u003eHowever, when building a custom car from the ground up, a deeper understanding of the power curve of an alternator is required.\u003c\/p\u003e\u003cp\u003eUsually, a performance alternator is used with a custom pulley or so-called 'power pulley' set.\u003c\/p\u003e\u003cp\u003eA mismatched pulley ratio and alternator will spell trouble, especially at idle speeds where performance is critical.\u003c\/p\u003e\u003cp\u003eTo avoid this, understanding the alternator's capability at slow speeds is important.\u003c\/p\u003e\u003cp\u003eAn alternator's output depends on speed, but this can be deceiving because this output is not linear.\u003c\/p\u003e\u003cp\u003eInstead, it follows a curve.\u003c\/p\u003e\u003cp\u003eEach alternator has a unique curve, and at idle, small changes in the alternator's speed can significantly affect its output capacity.\u003c\/p\u003e\u003cp\u003eBecause of this, pulley ratios are very important, especially when using high amperage alternators.\u003c\/p\u003e\u003cp\u003eThe pulleys supplied with the alternator are matched to the winding and power curve.\u003c\/p\u003e\u003cp\u003eIt is crucial that any dress-up pulley sets do not deviate from this ratio.\u003c\/p\u003e\u003cp\u003eTypically, a street-driven car should have a pulley ratio of at least 3:1.\u003c\/p\u003e\u003cp\u003eIf the vehicle has an automatic transmission with a low idle and spends a lot of time cruising, then a higher pulley ratio - perhaps 3.5:1 - should be used.\u003c\/p\u003e\u003cp\u003eAlternators can handle high speeds up to 20,000 RPMs for short periods, so overdriving the unit is not a problem.\u003c\/p\u003e\u003cp\u003eThe output of high amp alternators can drop off substantially under 2400 rotor RPMs.\u003c\/p\u003e\u003cp\u003eTherefore, Powermaster does not recommend power pulleys with high amp alternators.\u003c\/p\u003e\u003cp\u003ePowermaster employs a state-of-the-art computer alternator dyno to measure the performance of each alternator manufactured.\u003c\/p\u003e\u003cp\u003eOutput curves, engine idle speeds, and alternator pulley ratios are carefully considered to ensure good drivability at idle and slow cruising speeds.\u003c\/p\u003e","brand":"Powermaster","offers":[{"title":"Default Title","offer_id":51739590721818,"sku":"PRM31487","price":558.56,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/8942\/8506\/files\/71OpJPYvxWL.jpg?v=1771870748","url":"https:\/\/trybeepbeep.com\/products\/gm-powermaster-31487-chrome-220a-6-grv-alt","provider":"TryBeepbeep","version":"1.0","type":"link"}